Zooplankton Population Peaks And Their Temporal Occurrence In Bull Lake, Lincoln Co., Montana

Abstract

Samples of zooplankton were taken by vertical haul from Bull Lake, Lincoln Co., Montana, from early June to late August, 1987. Four genera of plankters and the nauplii of the copepods were monitored to determine the approximate time of maximum population densities. Results of the study showed that the total population was bimodal, with the first peak occurring June 20 in the adult plankters. The second population peaks occurred between July 25 and August 20; the exact date varied among the four species. Nauplii peaked June 7 and July 25. These temporal population changes are correlated to temperature and light-intensity data taken during sampling. A relationship between peak densities and these physical properties will predict population peaks for future seasons. This information would be used to estimate the proper time to plant fish in Bull Lake.